[9] RFR (S) 8147978: Remove Method::_method_data for C1

[John Rose]

On Feb 3, 2016, at 11:20 PM, Chris Plummer <chris.plummer at oracle.com> wrote:
> 
> Please review the following for removing Method::_method_data when only supporting C1 (or more specifically, when not supporting C2 or JVMCI). This will help reduce dynamic footprint usage for the minimal VM.

Even with C2 we could save footprint if we could merge the _method_data and _method_counters field.

Even on C1, with this change, we could save more footprint if we could make the _method_counters field a tagged union between a short count and the full method counters field, allocated lazily after (say) 10 iterations of a method.

The tracking bug for this is https://bugs.openjdk.java.net/browse/JDK-8013169 <https://bugs.openjdk.java.net/browse/JDK-8013169>

I just added a comment explaining the lazy allocation idea.

Any takers?

— John
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